My old practice (particularly D&D)
"You must gather your party before venturing forth." (instant "Like" for the first post to identify the source)
My new philosophy on staying with the party.
"Decide you must, how to serve them best." -Yoda
In a recent (d20) adventure (and by recent, within the past year), the players were trying to infiltrate an outlaw mining operation. Once they made it to a central computer port, the Tech Specialist remained there and aided the rest by interfering with and controlling various systems, even turning the turbolift into a martini shaker when reinforcements were trying to cut them off. I had the main group find new terminals, and hold position for the tech to "catch up" so they didn't get too separated, and the Tech's player was having enough fun with what he was doing that he realized he didn't need to stay with the group to "serve them best."
There have been situations where the group splitting up meant a player having to wait, especially when some skill uses took "minutes" while a combat round was a few seconds. (and this could even occur with everyone in the same room) The non-specified, but "about a minute" round for EotE makes it easier to switch back and forth between the two groups. It may get more separated if one group ends up in a fight while the other is still moving through corridors.
The key is to have enough "happenings" ready for both (all) groups. I've made a practice of keeping experience rewards pretty even for all players. When there's really great role playing, I give everyone a bonus, but I let the players know whom to thank. I will probably break from this in this system, since there's no real "levels", but the base XP for the session would be even, whether the character was in the thick of things, or running interference from a separate location.